Lane-change assistants, as they are commonly referred to, which are used to warn a driver of an approaching vehicle, in particular one approaching from behind, are generally known. In this context it is especially important to alert the driver to vehicles located in the blind spot of the own vehicle. With planar rearview mirrors, this blind spot or blind spot region of the vehicle results to the left and right rear for the driver, to the side of the vehicle. If a vehicle is overtaken, the driver of the overtaken vehicle is unable to see the overtaking vehicle for a few seconds unless he looks over his shoulder. Although mandatory when turning and when changing lanes, this particular glance over the shoulder is often omitted, especially also on highways. It is precisely during highway travel at a high speed that a lane change may have far-reaching consequences.
Overtaking, turning, entering and starting to drive are situations in which the rearview mirror is used and in which the glance over the shoulder is obligatory. At present systems are available which monitor the blind spot region to the left and right of the own vehicle. If a vehicle is located in these regions, the system warns the driver by an optic and/or acoustic signal. If this vehicle is moving in the same driving direction as the own vehicle, then oncoming vehicles or stationary objects will not be indicated, however.
As a rule, a warning is given for the most proximate object. In addition, it may optionally be provided to specify the dimension of the monitoring or recording range as a function of the speed of the vehicle. A display and warning with regard to objects that move only little relative to the vehicle is implemented on the basis of the surround sensor, e.g., ultrasonic sensors, starting at a specific speed when driving forward.
At present, sensors having different recording ranges are obtainable. Long range radar (LRR) has a wide range but is blind at close range. Ultrasonic sensors (USS) have high sensitivity at close range but only a limited range. It must be taken into account, however, that functions such as the lane change assistant require the combination of both characteristics since some vehicles approach at very high speeds. To trigger a timely warning, it is therefore necessary to detect the approaching vehicle early enough.
One possibility consists of using what is known as short range radar (SRR), which has a reach of up to 40 m. However, these sensors are relatively expensive and as yet have not received approval for the transmit frequency in Europe.
Thus, there is a need for a method and a system that allow the use of different sensors having different detection ranges and which are able to be utilized within the framework of an adaptive speed control.